1. Field of the Invention
The present invention relates to a method of a controlling pulse width modulated (PWM) inverter for use in induction motor drive and, more particularly, to a control method which allows a single PWM inverter to be used for the operation of induction motors having different rated voltages and different rated frequencies from those of the PWM inverter.
2. Description of the Prior Art
It is a common practice that a control unit of a PWM inverter is comprised of an arrangement of individual components such as logic gates, operational amplifiers, comparator circuits, etc., as shown in FIG. 1 of U.S. Pat. No. 3,624,486, issued Nov. 30, 1971, for example. The circuit condition of the device of this type is unconditionally determined by a rated voltage and a rated frequency of an induction motor as an object to be controlled. Therefore, for operation of induction motors having different ratings, PWM inverters exclusively designed for the respective individual motors must be provided. In other words, a single inverter was unable to be used in common for the induction motors having different ratings.